A radial piston hydraulic motor comprising a box frame with a cam ring connected thereto, pistons in a piston frame and press rollers in the pistons, which press rollers can be pressed by means of the pressure of a hydraulic fluid, such as hydraulic oil, against an inner surface of the cam ring. The piston frame comprises connections between the interior space and passages, and a shutter valve is provided within each connection for controlling the hydraulic fluid flow through the connection between the passages and the interior space. The shutter valve is arranged to allow hydraulic fluid to flow from the passage into the interior space, when the pressure in the working pressure inlet passage, in the return passage and in the interior space is equal, i.e. the motor is in free-rotating state.

A radial piston hydraulic motor comprising a box frame with a cam ring connected thereto, pistons in a piston frame and press rollers in the pistons, which press rollers can be pressed by means of the pressure of a hydraulic fluid, such as hydraulic oil, against an inner surface of the cam ring. The piston frame comprises connections between the interior space and passages, and a shutter valve is provided within each connection for controlling the hydraulic fluid flow through the connection between the passages and the interior space. The shutter valve is arranged to allow hydraulic fluid to flow from the passage into the interior space, when the pressure in the working pressure inlet passage, in the return passage and in the interior space is equal, i.e. the motor is in free-rotating state.

The invention relates to a radial piston hydraulic motor. The radial piston hydraulic motor comprises a cam ring provided, with a wave-shaped inner surface and radial cylinders provided in the inner part inside the cam ring and pistons that move therein as well as rollers coupled to the pistons so as to follow the inner surface of the cam ring. By the effect of the working pressure of hydraulic oil conveyed to the cylinders, the rollers that are pressed against the inner surface of the cam ring provide a rotating movement of the cam ring and the inner part relative to each other. The hydraulic motor is provided with disengaging members disengaging the rollers coupled to the pistons from contact to the inner surface of the cam ring when the working pressure stops acting in the cylinders for bringing the hydraulic motor into freewheeling. The hydraulic motor is provided with a control coupling which, when the prevailing pressure of hydraulic oil in the working pressure line that leads to the cylinders drops below a specific level, automatically disengages the cylinders from the working pressure line and couples the hydraulic motor into freewheeling.